The pleasures of owning and operating marine craft having inboard engines are tempered by the problem of marine growth, more specifically barnacles, on the underwater hull and on the shaft transmitting power from the engine to the propeller attached to the end of the shaft.
Marine growth is most severe on craft operating in salt water. Anti-fouling coatings on the part of the hull which is underwater minimize or substantially eliminate such growth on those surfaces. A method of eliminating marine growth on the metal propeller shaft has not yet been found. The growth impedes the efficiency of the marine engines on such equipped craft because the build up of the growth causes excessive turbulence along the shaft, thereby reducing the efficiency of the associated propeller. To maintain maximum efficiency from the powered propulsion system, the marine growth should be removed every few weeks when the boat is in use. The usual procedure is to remove the craft from the water, or send a diver down to remove the growth while the craft is yet in the water.
At the present time, the principal tool used to remove marine growth from the propeller shaft is a putty knife. The steel in the putty knife blade is very durable and the thinness of the blade attacks the adhering marine growth very well. However, a putty knife is unwieldy and inefficient to use because of the placement of the handle in relation to the scraping edge, and because of the shape of the scraping edge. Because the blade of the putty knife is flat, but the shaft is round, the putty knife often slips off the shaft, frequently injuring the user, and ridges of marine growth are usually left on the shaft.